Hitherto-known nanostructures containing carbon atoms include carbon nanotubes made of a cylindrically rolled two-dimensional graphene sheet, and cyclic carbon nanotubes made of such carbon nanotubes.
Carbon nanotubes have extremely high mechanical strength and high temperature resistance, and efficiently discharge electrons under voltage application. With these advantageous properties, carbon nanotubes are expected to be applied to various fields, including chemistry, electronics, and life science.
Known methods of manufacturing carbon nanotubes include arc discharge, laser furnaces, chemical vapor deposition, and the like. However, these methods have a disadvantage in that they can only produce mixtures of carbon nanotubes with various diameters and lengths.
As a replacement for tubular nanostructures such as carbon nanotubes having a certain length derived from a continuous linkage of carbon atoms, recent studies have focused attention on cyclic nanostructures. For example, cycloparaphenylene (CPP) is a simple and beautiful molecule in which benzenes are linked at the para-positions to form a circle. Recent studies have revealed that cycloparaphenylene has a significantly distinctive structure and nature. In particular, since CPP has various diameters depending on the number of benzene rings contained therein, and thereby has various natures, if CPP is selectively produced, it has the potential to produce carbon nanotubes having various diameters. Therefore, the thoroughly selective production of CPP having different numbers of benzene rings has been desired. However, although a method for obtaining CPP as a mixture is known, the selective synthesis of CPP was successful in only a few cases.
The present inventors succeeded in the synthesis of various cycloparaphenylene compounds through a method using a cyclic cycloparaphenylene precursor that contains a cyclohexane ring as a flexural portion (Patent Documents 1 and 2, Non-Patent Document